Vibration damping apparatus

ABSTRACT

Disclosed is a vibration damping apparatus incorporated in the crossing of diagonal members such as braces of a framed structure for damping vibration imparted by external force such as an earthquake or a strong wind. The apparatus comprises a plurality of rotatable members or discs, a resistive body disposed between the discs, and a pair or pairs of link bars causing relative rotation of the discs in response to the impartation of the external force, whereby the vibration is damped by the resistance force of the resistive body resisting to the external force.

BACKGROUND OF THE INVENTION

This invention relates to a vibration damping apparatus, and moreparticularly to an apparatus of the kind above described which issuitable for incorporation in diagonal members such as braces used in aframework of a framed construction.

In a framed construction such as a steel tower, a tall platform or atall building, impartation of horizontal or lateral vibration theretoproduces alternately a tensile force and a compressive force in diagonalmembers crossing each other.

The vibration damping apparatus according to the present invention issuitable for application to such a framed structure in that it resistsagainst deformation of the diagonal members in the plane of theframework due to such stresses, for example, relatively abruptdeformation of the diagonal members due to an earthquake or a strongwind and absorbs the horizontal vibration imparted to the framedstructure to damp the amplitude of vibration thereby making the framedstructure vibration-proof.

BRIEF SUMMARY OF THE INVENTION

It is a first object of the present invention to provide a vibrationdamping apparatus which comprises a plurality of rotatable members, aresistive body disposed between these rotatable members, and a pluralityof link bars causing relative motion of the rotatable members, and inwhich a material having a high viscosity is used as the resistive bodyto utilize the viscous shearing resistance of the highly viscousmaterial for vibration damping.

A second object of the present invention is to provide a vibrationdamping apparatus which comprises a plurality of rotatable members, aresistive body disposed between these rotatable members, and a pluralityof link bars causing relative motion of the rotatable members, and inwhich a resilient member is used as theresistive body to utilize thedeformation resistance of the resilient member for vibration damping.

A third object of the present invention is to provide a vibrationdamping apparatus which comprises a plurality of rotatable members, aresistive body disposed between these rotatable members, and a pluralityof link bars causing relative motion of the rotatable members, and inwhich a material having a high viscosity is used in combination with aresilient member to provide the resistive body so as to utilize theviscous shearing resistance of the highly viscous material and thedeformation resistance of the resilient member for vibration damping.

According to the present invention, there are at least two rotatablemembers disposed opposite to each other so as to be rotatable around thesame axis of rotation while defining a very small gap therebetween.

Unless otherwise desired, the rotatable members are generally providedin the form of discs having their centers aligned on the same axis ofrotation, since the opposing surfaces of the members, especially, theeffective surface areas of the members having the resistive body(described later) disposed therebetween are preferably circular from theaspects of design, manufacture and handling.

The adjoining ones of these rotatable members rotate in directionsopposite to each other around the common axis of rotation in response toimpartation of turning force from the line bars which will be describedin detail later.

When the number of the rotatable members is two, they rotate indirections opposite to each other, and when the number of the members isthree or more, they rotate alternately in directions opposite to oneanother. More precisely, when the number of the members is three ormore, the alternate ones of them rotate in a group in a directionopposite to the direction of rotation of the remaining one or a group ofthe remaining ones.

The rotatable members belonging to each of groups may be connectedtogether by suitable connecting means, and one of the link bars may becoupled to the connecting means connecting each group of the rotatablemembers to permit relative rotation of the rotatable members. This is apreferred mode especially when the number of the rotatable members ismore than three.

At least two link bars constitute a link bar group, and these link barsare coupled to the rotatable members by one of two methods. According tothe first method, the link bars are pivoted at one end thereof to eachother by a pin and are directly coupled to the respective rotatablemembers at the other end thereof so as to function as openable legs.Alternatively, the link bars are indirectly coupled to the rotatablemembers through connecting means each of which connects alternate onesof the rotatable members as a group.

Only one group of the link bars may be coupled to the rotatable members,or two groups may be disposed in a relation diametrically opposite toeach other in the diametrical direction of the rotatable members, orfour groups of similar arrangement may be disposed. However, thearrangements above described are not necessarily required depending onthe application.

The link bars in the same group or in all the groups need not have thesame length. The link bars of such lengths may be coupled to therotatable members in such a relation that the line bisecting the angledefined between the openable legs of the link bars passes at leastthrough the common center of rotation of the rotatable members.

In such a mode, however, those rotatable members rotating in thedirections opposite to each other may not rotate with a uniform rotationangle and a uniform angular velocity, and the amount and rate ofdisplacement of the pivoted end of one of the link bar group movabletoward and away from the common center of rotation of the associatedrotatable members may be different from those of the pivoted end ofanother link bar group. Further, these differences and the degreethereof are governed by the combination of the shorter ones of thedrivers and followers including the common center of rotation of therotatable members and the pivoted end of the link bars in the quadriccrank mechanisms constituted by the link bar groups and the associatedrotatable members.

Therefore, it is more practical and preferable from the aspect of designthat the link bars in the same group or in all the groups have the samelength, and the line bisecting the angle defined between the openablelegs of the link bars passes through the common center of rotation ofthe rotatable members.

According to the second method, four link bars are employed and arepivoted to each other by pins at their ends so as to constitute aquadric crank mechanism which can turn around the axes of the pins. Thetwo link bars disposed opposite to each other among the four link barsare coupled at their middle points to the corresponding points of one oftwo rotatable members respectively, which points are located near theperiphery of the roatable member and spaced apart by the same distancefrom the center of rotation of the rotatable member, or such link barsare coupled at their middle points to connecting means connectingtogether, as a group, the alternate ones of the rotatable membersrotating in the same direction. Similarly, the remaining two link barsdisposed opposite to each other are coupled at their middle points tothe corresponding points of the other rotatable member respectively,which points are located near the periphery of the rotatable member andspaced apart by the same distance from the center or rotation of therotatable member, or such link bars are coupled at their middle pointsto connecting means connecting together, as a group, the alternate onesof the rotatable members rotating in a direction opposite to thedirection of rotation of the former group.

In such an assembly of the quadric crank mechanism and rotatablemembers, deformation of the quadric crank mechanism can be convertedinto relative rotation of the rotatable members in the oppositedirections, provided that the distance between the center of rotation ofeach of the rotatable members and the coupled point at the middle ofeach of the link bars is equal to the distance between the coupled pointand the pivoted points of each of the link bars.

According to the present invention, the resistive body disposed betweenthe rotatable members is preferably a material having a high viscosity,a resilient member or the combination of them.

The highly viscous material is filled or charged in the very small gapdefined between the rotatable members. As preferred examples of thehighly viscous material to be employed in the present invention,high-molecular fluid materials, for example, liquid polyolefines, liquidpolysiloxane and hydrocarbons such as tars can be cited. A highlyviscous material having a coefficient of viscosity as high as severalthousand or several ten thousand poises is especially recommended foruse in a vibration damping apparatus incorporated in diagonal members ofa framed structure.

The viscous shearing resistance force F of a highly viscous materialfilled or charged in a gap between plates is generally expressed as

    F=KS(V/C).sup.m

where S is the area of the opposing surfaces of the plates (thesubstantially effective areas holding the highly viscous materialtherebetween), V is the velocity of relative movement of the plates (thevelocity of vibration), C is the dimension of the gap between theplates, K is a constant determined by the coefficient of viscosity ofthe viscous material used, and m is a coefficient determined by theproperty of the viscous material.

Each of the fluid materials above cited exhibits the behaviour ofnon-Newtonian flow. The inventors have experimentally confirmed that thevalue of m of such a material is less than unity (1) and, especially, inthe case of a liquid polyolefine, the value of m is close to 0.5.

It will be understood from the expression F=KS(V/C)^(m) that the highlyviscous material generates a resistance force F proportional to the m-thpower of the velocity of the plates moving relative to each other. Thevalue of m less than unity (1) indicates that the curve of resistanceforce rises exponentially with time, and this means that the vibrationdamping apparatus can reliably and stably produce the resistance forceresisting the momentary and abrupt vibration caused by, for example, anearthquake.

When such a highly viscous material is filled or charged in the verysmall gap defined between the rotatable members, the viscous shearingtorque T produced due to the relative rotation of the rotatable membersis expressed as ##EQU1## where ω is the relative angular velocity of therotatable members, r₀ is the outer diameter of the viscous shearingarea, r₁ is its inner diameter, and K and m are the constants definedhereinbefore. It will thus be seen that relative rotation of therotatable members produces a torque T proportional to the m-th power ofthe relative angular velocity ω.

The resilient member employed in the present invention is preferably inthe form of resilient rubber or a spring. Such a resilient member isdisposed between the rotatable members rotating in the directionsopposite to each other so as to impart a predetermined restraining forcerestraining the relative movement of the rotatable members.

The resilient member of rubber is, for example, in the form of anannular rubber ring having a rectangular cross section. Such a ring issecured at its side surfaces to the corresponding portions of theopposing surfaces of the rotatable members as by an adhesive while itsinner and outer peripheral surfaces are not restrained to be left free,or such a ring is secured at its inner and outer peripheral surfaces todiametrically opposite annular surface portions previously formed in theopposing surfaces of the rotatable members, as by an adhesive, while itsside surfaces are not restrained to be left free.

In order to facilitate securing of the resilient member of rubber to therotatable members and also to produce a uniform torsional shearingstress in the resilient member of rubber, sheets such as thin metalsheets may be integrally molded on the side surface or inner and outerperipheral surfaces of the rubber ring during vulcanization, and therubber ring may then be bonded to the rotatable members through the thinmetal sheets. This is one of recommended means.

Another mode may be employed in which concavities, convexities or anyother engaging means may be provided on these thin metal sheets for thepurpose of mechanical engagement with the rotatable members. Therequirement is that a resiliently deformable portion is left in theresilient member of rubber, and the remaining portion of the resilientmember of rubber is secured to the relatively-rotating rotatable membersto restrain the relative motion of the rotatable members, therebyproducing a torsional shearing stress in the resilient member of rubber.

The torsional shearing force F of the resilient member of rubber isexpressed as

    F=1/2·φ·α·K.sub.φ

where φ is the rotation angle, α is a constant determined by thedimensions and mounting angle of the ring, and K.sub.φ is a springconstant of the resilient member.

Thus, the force F proportional to the rotation angle φ, hence, the forcecorresponding to the "displacement" (moved distance) of the rotatablemembers is produced.

Another resilient member is a spring in the form of a metal ring havingpart of its ends suitably cut out.

Such a spring is so disposed that one of the cut-out ends is anchored bysuitable means to one of the rotatable members, and the other of thecut-out ends is also anchored by suitable means to the other rotatablemember.

The ring spring may be such that the cut-out ends lie on the samecircumference or cross each other in the cirumferential direction in aspiral fashion.

The resilient member in the spring form also produces the force Fproportional to the rotation angle, hence, the force corresponding tothe "displacement" (moved distance), as in the case of the resilientmember of rubber.

The resilient member differs from the aforementioned highly viscousmaterial in that it imparts a restoring force to the rotatable lmemberswhen the latter have rotated through a predetermined angle.

Therefore, the highly viscous material and the resilient memberembodying the two forms of the resistive body may be singly employed ormay be employed in combination to suit specific applications consideringtheir properties. Therefore, it is preferable to employ the combinationof these resistive bodies when the vibration damping apparatus isspecifically incorporated in diagonal members of a framed structureusing such diagonal members.

Other objects, features and advantages of the present invention will beapparent to those skilled in the art from the following detaileddescription of preferred embodiments thereof taken in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a first embodiment of thevibration damping apparatus according to the present invention.

FIG. 2 is a schematic perspective view of a second embodiment of thepresent invention.

FIG. 3 is a schematic perspective view of a third embodiment of thepresent invention.

FIG. 4 is a schematic perspective view of a modification of the thirdembodiment shown in FIG. 3.

FIGS. 5 and 6 are diagrammatic views of modifications of the apparatusshown in FIGS. 3 and 4, respectively.

FIG. 7 is a longitudinal sectional view of a modification in which thecommon center of rotation of the rotatable members or discs is fixed toa stationary member.

FIG. 8 is a schematic perspective view of a fourth embodiment of thepresent invention which includes three discs.

FIG. 9 is a schematic perspective view of part of a modification of thefourth embodiment shown in FIG. 8.

FIG. 10 is a schematic perspective view of a fifth embodiment of thepresent invention which includes four discs.

FIG. 11 is a front elevation view of a sixth embodiment of the presentinvention, showing a more practical form of the third embodiment shownin FIG. 4.

FIG. 12 is a sectional view of the sixth embodiment of the presentinvention taken along the line XII--XII in FIG. 11.

FIG. 13 is a schematic front elevation view of a frame structureincluding the apparatus according to the present invention therein.

FIG. 14a is a sectional view of a seventh embodiment of the presentinvention.

FIG. 14b is a sectional view of an eighth embodiment of the presentinvention.

FIG. 15 is a sectional view of part of the apparatus to illustrateanother manner of disposition of the annular resilient member of rubberin the seventh embodiment of the present invention shown in FIG. 14a.

FIG. 16 is a plan view of part of a modification of the seventhembodiment shown in FIG. 14a, in which the resilient member of rubber isreplaced by a spring which is generally annular in shape.

FIG. 17 is a sectional view taken along the line XVII--XVII in FIG. 16.

FIG. 18 is a plan view of part of a modification of the apparatus shownin FIGS. 15 and 16, in which a spiral spring is used.

FIG. 19 is a sectional view taken along the line XIX--XIX in FIG. 18.

FIG. 20 is a schematic front elevation view of a ninth embodiment of thepresent invention illustrating a manner of coupling between a quadriccrank mechanism and rotatable members.

FIG. 21 is a partial front elevation view showing a modification of FIG.20, in which another manner of coupling slightly different from thatshown in FIG. 20 is illustrated for only one of the link bars.

FIG. 22 is a front elevation view of a tenth embodiment of the presentinvention which is used in the cross point between diagonal members of aframed structure.

FIG. 23 is a sectional view taken along the line XXIII--XXIII in FIG.22.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic perspective view of a first embodiment of thevibration damping apparatus according to the present invention whichcomprises two rotatable members or discs, and a pair of link bars ofequal length coupled to the discs in such a relation that the linebisecting the angle defined between the openable legs of the link barspasses through the common center O of rotation of the discs. The discsare supported at their common central axis on another member which isstationary, and a load is imparted to the pivoted point P of the discs.

Referring to FIG. 1, a pair of link bars 1a and 1b of equal length arepivoted to each other at a point P and coupled to two discs 2a and 2brespectively. Impartation of a force to the pivoted point P in adirection shown by the arrow A urges the point P in the same direction,and a force tending to close the openable legs of the link bars actsupon the link bars 1a and 1b. Consequently, the discs 2a and 2b coupledto the link bars 1a and 1b respectively are rotated in directionsopposite to each other, that is, in directions shown by the arrows C andD respectively around their common central axis O. On the other hand,impartation of a force to the point P in a direction shown by the arrowB urges the point P in the same direction, and a force tending to openthe openable legs of the link bars acts upon the link bars 1a and 1b, sothat the discs 2a and 2b are rotated in directions opposite to eachother, that is, in directions shown by the arrows E and F respectivelyaround the common central axis O. A resistive body is disposed in a verysmall gap defined between the discs 2a and 2b.

Thus, a crank mechanism is formed in which the link bars 1a, 1b functionas the driver and the discs 2a, 2b function as the follower. Theopen-close motion of the link bars functioning as the driver isconverted into relative rotation of the discs functioning as thefollower. As a result of this relative rotation, a resistance force isgenerated by the resistive body disposed in the gap between the discs 2aand 2b functioning as the follower, thereby damping the amplitude ofvibration imparted to the pivoted point P of the link bars 1a and 1bfunctioning as the driver.

FIG. 2 is a schematic perspective view of a second embodiment of thevibration damping apparatus according to the present invention in whichtwo pairs of link bars 1a, 1b and 1c, 1d are disposed opposite to eachother in the diametrical direction of two discs 2a and 2b, and theopenable legs of one of the pairs of the link bars extend in the samedirection as the direction of extension of the corresponding openablelegs in the other pair. In the second embodiment shown in FIG. 2, thedisc 2a and 2b may be or may not be supported at their common centralaxis O on another member which is stationary.

FIG. 3 is a schematic perspective view of a third embodiment of thevibration damping apparatus according to the present invention whichcomprises two discs 2a, 2b and four pairs of link bars 1a, 1b; 1c, 1d;1e, 1f; and 1g, 1h. In the third embodiment shown in FIG. 3, the twolink bar pairs among the four pairs are disposed opposite to each otherin the diametrical direction of the discs 2a and 2b, and the remainingtwo link bar pairs are also similarly disposed. The openable legs of thelink bars in the two opposing pairs extend in the same directions asdescribed with reference to FIG. 2, but those of the adjoining link barsin the different pairs extend in different directions as seen in FIG. 3.

The line connecting between the pivoted points of the two opposing linkbar pairs crosses at right angles with that connecting between thepivoted points of the remaining two opposing link bar pairs in FIG. 3. Amodification of the third embodiment is shown in FIG. 4 in which it willbe seen that the ends of the openable legs of the adjoining link bars inthe different pairs are coupled by pins to the same discs respectively.

In the embodiments shown in FIGS. 3 and 4 too, the discs 2a and 2b maybe or may not be supported at their common central axis O on anothermember which is stationary. Especially, when the pivoted point of eachlink bar pair is coupled to the cross point of two diagonal members in aframed structure, it is preferable that the common center O of rotationof the discs is supported in space by the diagonal members under tensionwithout supporting it on another stationary member.

In such embodiments of the present invention applied to the cross pointof the two diagonal members, the incorporation of the apparatus at thecross point would not lead to an unbalance between the tensions of thetwo diagonal members during the stage of erection in which the tensionis imparted to each of the diagonal members. This is because one of thediscs rotates through a very small angle relative to the other in eitherdirection to maintain constant the tensions of the diagonal members.

FIGS. 5 and 6 are diagrammatic views showing modifications of theembodiments shown in FIGS. 3 and 4 respectively. It will be seen inFIGS. 5 and 6 that the lines X and Y connecting between the opposinglink bar pairs do not cross at right angles with each other.

In such embodiments, one of the link bars in the pair defining an acuteangle therebetween and the adjoining one in the similar pair may becoupled to the same disc by a common pin.

FIG. 7 shows a modification in which the discs 2a and 2b are supportedat the common center O of rotation on another member 7 which isstationary.

FIG. 8 is a schematic perspective view of a fourth embodiment of thevibration damping apparatus according to the present invention whichcomprises three discs 2a, 2b, 2c and two pairs of link bars 1a, 1b and1c, 1d. The link bar pairs are disposed opposite to each other in thediametrical direction of the discs.

In this fourth embodiment, each of the three discs 2a, 2b and 2c isprovided with a pair of diametrically opposing ears 8. The two discs 2aand 2b among the three are disposed opposite to each other with theirears 8 aligned with each other, and these discs 2a and 2b are connectedto each other by pins J₁ extending through the ears 8 respectively. Theremaining disc 2c is interposed between the two discs 2a and 2b in sucha relation that the ears 8 of the former are situated intermediatebetween the ears 8 of the latter. The openable legs of the link bars 1aand 1c are coupled at their free ends to the ears 8 of the discs 2a and2b by the pins J₁ respectively, while the openable legs of the link bars1b and 1d are coupled at their free ends to the ears 8 of the centraldisc 2c by pins J₂.

FIG. 9 shows a modification of the embodiment shown in FIG. 8. Thismodification comprises three link bars 1a, 1a' and 1b. The openable legsof the link bars 1a and 1a' are coupled at their free ends to the discs2a and 2b disposed with their ears 8 aligned with each other,respectively, while the openable leg of the link bar 1b is coupled atits free end to the ear 8 of the central disc 2c.

In the embodiments shown in FIGS. 8 and 9, the resistance of theresistive body occurs at the two interfaces of the three discs.Therefore, the resistance force exhibited by the combination is twotimes as large as that of the combination of two discs having the sameeffective area.

FIG. 10 is a schematic perspective view of a fifth embodiment of thevibration damping apparatus according to the present invention whichcomprises four discs 2a, 2b, 2c, 2d and two pairs of link bars 1a, 1band 1c, 1d disposed opposite to each other in the diametrical directionof the discs. Referring to FIG. 10, the discs 2a and 2c rotate in a pairin one direction, while the discs 2b and 2d rotate in a pair in adirection opposite to the direction of rotation of the discs 2a and 2c.It will be readily seen that the resistance force exhibited by such acombination is three times as large as that exhibited by the combinationof two discs.

FIG. 11 shows a sixth embodiment or a more practical form of theembodiment shown in FIG. 4, when applied to the cross points of diagonalmembers in a framed structure. FIG. 12 is a sectional view taken alongthe line XII--XII in FIG. 11.

In FIGS. 11 and 12, reference numerals 1, 2 and 3 designate generallylink bars, discs and a resistive body which is a material having a highviscosity in this embodiment, respectively.

Referring to FIGS. 11 and 12, two pairs of link bars 1a, 1b and 1c, 1dare disposed opposite to each other in the diametrical direction of thediscs 2 for making open-close movement. Other two pairs of link bars 1e,1f and 1g, 1h are similarly disposed opposite to each other in thediametrical direction orthogonal with respect to the direction of theformer two pairs for making open-close movement opposite to that of theformer two pairs.

The link bars 1a, 1c, 1e and 1g are pivoted to the link bars 1b, 1d, 1fand 1h by pivot pins 10, 11, 12 and 13, respectively, and these pivotpins 10, 11, 12 and 13 are received in sleeves 14, 15, 16 and 17respectively. The free ends of the openable legs of the link bars 1a, 1fand 1c, 1h are coupled to one of the discs or disc 2a by pivot pins 18respectively, and, similarly, the free ends of the openable legs of thelink bars 1b, 1g and 1d, 1e are coupled to the other disc 2b by pivotpins 19 respectively.

A pin 20 extends through the common center of rotation of the discs 2aand 2b and is fixed in position by nuts 21. A spacer 22 is fitted on thepin 20 between the discs 2a and 2b to maintain a very small gap betweenthe two discs 2a and 2b. These two discs 2a and 2b can rotate around theaxis of the pin 20.

The resistive body or highly viscous material 3 is injected and filledin the very small gap through ports 23, and these ports 23 are closed byplugs after the material 3 has been completely charged to uniformly fillthe very small gap defined between the discs 2a and 2b. In lieu ofcharging the highly viscous material 3 through the ports 23, thematerial 3 may be previously coated on the required areas of the discsurfaces during the step of assembling of the discs without providingthe ports 23. It is especially desirable that the highly viscousmaterial 3 be bubble-free and uniformly charged in the very small gapbetween the discs 2a and 2b.

A seal ring 4 is disposed to cover the outer peripheries of the opposingsurfaces of the discs 2a and 2b to seal the very small gap definedbetween the disc 2a and 2b.

Diagonal members 5 such as braces are coupled to the sleeves 14 and 15respectively, and similar diagonal members 6 are coupled to the sleeves16 and 17 respectively.

FIG. 13 is a schematic front elevation view of a frame structure toillustrate that the vibration damping apparatus Q according to thepresent invention are disposed in the framework of the framed structure.

When deformation occurs in the plane including the diagonal members 5and 6 due to, for example, an earthquake, a tensile force is impartedto, for example, the diagonal members 5, and a compressive force isimparted to, for example, the diagonal members 6, thereby producing astress in these diagonal members 5 and 6. In such a case, the link barsin each of the vibration damping apparatus Q act to rotate the two discsin directions opposite to each other, and the viscous torsionalresistance force produced in the highly viscous material charged in thevery small gap defined between the discs acts to alleviate the vibrationof the framed structure.

It will be seen from the aforementioned embodiments that the vibrationdamping apparatus of the present invention comprises link barsfunctioning as a driver and discs coupled to the link bars to functionas a follower. The discs constituting the follower are rotated indirections opposite to each other in response to the open-close movementof the link bars constituting the driver. Therefore, when theembodiments of the present invention are compared with, for example, aprior art vibration damping apparatus in which one of two discs acts asa stationary resistive member and the other acts as a relativelyrotatable resistive member, the discs constituting the driver can makerelative rotation through a rotation angle which is substantially twotimes as large as that of the prior art apparatus, and slight movementof the driver can efficiently provide a great resistance to vibration.

Further, the vibration damping apparatus of the present invention isdistinguished from another prior art vibration damping apparatus ofdashpot type in which flow of a fluid material (a viscous material)caused as a result of impartation of an internal pressure to thematerial itself is utilized for vibration damping. Further, because ofthe fact that the viscous material employed in the present invention hasa high viscosity, there is substantially no possibility of leakage ofthe viscous material to the exterior from the vibration dampingapparatus. Therefore, the structure need not be strictlypressure-resistive or fluid-tight, and the vibration damping apparatusof simple construction can efficiently attain the desired object.

FIG. 14a shows a seventh embodiment, and reference numerals 1a to 23designate the same parts as those appearing in FIGS. 11 and 12, and anydetailed description thereof is unnecessary.

The embodiment shown in FIG. 14a is featured by the use of a resilientmember 40 in addition to the highly viscous material as the resistivebody 3. This resilient member 40 is illustrated in the form of anannular resilient member of rubber in FIG. 14a. This annular resilientmember 40 includes a rubber ring 41 and a pair of annular reinforcingplates of metal 42 secured integrally to the both side surfacesrespectively of the rubber ring 41.

Such an annular resilient member 40 is fixedly positioned in the annulargroove formed in the outer peripheral area of the disc assembly with thereinforcing metal plates 42 bonded to the walls of the groove as by anadhesive. In response to impartation of vibration due to, for example,an earthquake, a torsional sheering stress is produced in the annularresilient member 40, and a viscous sheering resistance force is producedin the highly viscous material 3 charged in the very small gap definedbetween the discs 2a and 2b, thereby damping and alleviating thevibration of the framed structure.

FIG. 14b shows an eighth embodiment, and reference numerals 1a-21designate the same parts as those appearing in FIGS. 11 and 12, and anydetailed description thereof is unnecessary.

The embodiment shown in FIG. 14b is featured by the use of a resilientmember 40' as the resistive body, instead of the high viscous material 3shown in FIG. 14a. The resilient member 40' includes a rubber body 41'and a pair of reinforcing plates of metal 42' secured integrally to theboth side surfaces respectively of the rubber body 41' and also to thediscs 2a, 2b.

FIG. 15 is a sectional view of part of the apparatus to illustrateanother manner of disposition of the annular resilient member 40 in theembodiment of the present invention shown in FIG. 14a.

FIGS. 16 and 17 show a modification of the embodiment shown in FIG. 14a,in which the annular resilient member of rubber is replaced by a spring40 which is generally annular in shape. Referring to FIGS. 16 and 17,the generally annular spring 40 is anchored at one end thereof to thedisc 2a by a pin 43 and at the other end thereof to the other disc 2b bya pin 44. In this modification too, the spring 40 is as effective as theannular resilient member of rubber employed in the embodiment shown inFIG. 14a.

FIGS. 18 and 19 show a modification of the embodiment shown in FIGS. 16and 17. In the modification shown in FIGS. 18 and 19, the annular springis replaced by a spiral spring 40 making a plurality of turns betweenthe discs 2a and 2b, so that it has sufficient margin in its resiliency.

The embodiments shown in FIGS. 14a to 19 employ the combination of thehighly viscous material and the resilient member. Therefore, when therate of deformation occuring in the plane of the framework of a framedstructure is very slow, the combination of the highly viscous materialand the resilient member permits deformation under a certain constantrestraining force, while when the rate of deformation is relativelyrapid as when deformation is caused by, for example, an earthquake or astrong wind, the combination of the highly viscous material and theresilient member produces a great resistance force thereby absorbing thehorizontal or lateral vibration imparted to the framed structure andsufficiently damping the amplitude of vibration so as to enhance theresistance to vibration.

FIGS. 20 to 23 show a ninth embodiment, its modification, a tenthembodiment and its modification, respectively. In the embodiments, fourlink bars are pivoted to each other at their ends by pivot pins toconstitute a quadric crank mechanism capable of turning around the axesof the pivot pins.

A plurality of rotatable members or discs are combined with these linkbars. The two link bars disposed opposite to each other among the fourlink bars are coupled at their middle points to the corresponding pointsof one of two discs respectively, which points are located near theperiphery of the disc and are spaced apart by the same distance from thecenter of rotation of the disc, or such link bars are coupled at theirmiddle points to connecting means connecting together, as a group, thealternate ones of the discs rotating in the same direction. Similarly,the remaining two link bars disposed opposite to each other are coupledat their middle points to corresponding points of the other discrespectively, which points are located near the periphery of the discand are spaced apart by the same distance from the center of rotation ofthe disc, or such link bars are coupled at their middle points toconnecting means connecting together, as a group, the alternate ones ofthe discs rotating in a direction opposite to the direction of rotationof the former group. This embodiment differs from the aforementionedembodiments in the arrangement just described.

In such an assembly of the quadric crank mechanism and discs in thisembodiment, deformation of the quadric crank mechanism can be convertedinto relative rotation of the discs in the opposite directions, providedthat the distance between the center of rotation of each of the discsand the coupled point at the middle of each of the link bars is equal tothe distance between the coupled point and the pivoted points of each ofthe link bars.

If the dimensional relation above described were not satisfied, it wouldbe unable, theoretically, to convert the deformation of the quadriccrank mechanism into the relative rotation of the discs. In other words,it is impossible to cause deformation of the quadric crank mechanismitself.

Therefore, a coupling arrangement satisfying such a condition isgenerally employed in this embodiment, as schematically illustrated inFIG. 20.

Referring to FIG. 20, four link bars B₁, B₂, B₃ and B₄ of equal lengthare pivoted to each other at points Q₁, Q₂, Q₃ and Q₄. The link bar B₁is coupled at its middle point P to one of two discs or disc A by a pin.Symbol O designates the center of rotation of the disc A, and therelation OP=PQ₁ (=PQ₂) is satisfied. Suppose now that the points Q₁ andQ₃ move on the axis Y--Y in a direction shown by the arrow, and thepoints Q₂ and Q₄ move on the axis X--X in a direction shown by thearrow, thereby causing deformation of the quadric crank mechanism. The,the point P describes an arc e of radius OP around the center ofrotation of the disc A.

In this connection, it is not correct to conclude that the combinationof the crank mechanism and the disc would not satisfactorily operateunless the aforementioned dimensional relation is satisfied even when avery limited condition is given.

This will be explained with reference to FIG. 21 in which the link barB₁ is replaced by a link bar B₁ ' and the distance PQ₁ ' (=PQ₂ ') is,for example, larger by about 30% than the distance OP.

Suppose now that points Q₁ ' and Q₂ ' in FIG. 21 move on the X--X axisand Y--Y axis in the directions shown by the arrows respectively. Unlikethe case of FIG. 20, the point P does not describe the arc e whoseradius is OP. In the case of FIG. 21, the point P describes a locus e'which deviates outward from the arc e. Therefore, the coupled assemblyof the link bars and the discs shown in FIG. 21 is theoretically unableto satisfactorily operate, but, actually, it can effectively operatewithin a certain limited range.

The reason will now be explained. The degree of deviation of the locuse' from the arc e is dependent upon the dimensional difference betweenOP and PQ₁ ' (PQ₂ ') and upon the displacement of the point P in thecircumferential direction (the rotation angle of OP). Since the lengthof PQ₁ ' (PQ₂ ') is larger by about 30% than that of OP, and therotation angle of OP is about 10° (about 20° in terms of the relativerotation angle of the two discs), the locus e' is very close to the arce.

Further, at the relatively turnable connections such as the pivotedconnections between the link bars and the coupled connections betweenthe link bars and the discs, a suitable clearance is provided betweenthe pin and the pin-ceceiving hole in all of the connections to ensuresmooth turning of the former relative to the latter.

Therefore, under a very limited condition, slight deviation of the locuse' from the arc e is absorbed by the clearance provided in therelatively turnable connections so that the coupled assembly caneffectively operate under such a limited condition. This clearance maybe similar to that commonly employed in a fit between mechanical partsand thus need not be excessively larger than required, because anunnecessarily large clearance will give rise to rather a bad result.

An example of the present embodiment of the vibration damping apparatusapplicable under such a very limited condition is that used in thecrossing of diagonal members of a framed structure.

The combination of the link bars and the discs shown in FIG. 21 providesthe following advantages among other:

(1) The pivoted points Q' can be located at positions more distant inthe radial direction from the periphery of the disc A than in the caseof FIG. 20 when the point P is spaced from the center O by the samedistance as that in FIG. 20. Therefore, the rotation torque is notsubstantially reduced, and the freedom of deformation of the crankmechanism can be made greater. (It will be pointed out in thisconnection that the freedom of deformation of the crank mechanism shownin FIG. 20 is extremely limited.)

(2) The assembly can be so configured as to improve the rigidity of thelink bars.

In this embodiment too, the resistive body disposed between the discs isa material having a high viscosity or a resilient member or thecombination of the highly viscous material and the resilient member.

FIG. 22 is a front elevation view of a more practical form of the aboveembodiment, and FIG. 23 is a sectional view taken along the lineXXIII--XXIII in FIG. 22.

This tenth embodiment exhibits substantially the same function as thatexhibited by the seventh embodiment shown in FIG. 14a, and, therefore,like reference numerals are used in FIGS. 22 and 23 to designate like orequivalent parts appearing in FIG. 14.

Link bars 1a', 1b', 1c' and 1d' have the same length, and these linkbars are pivoted at their ends to each other by pivot pins 10, 11, 12and 13 as shown.

These four link bars 1a', 1c' and 1b', 1d' of the same length arecoupled at their middle point to two discs 2a and 2b by coupling pins 18and 19 respectively, so that the link bars can turn around the axes ofthe couling pins respectively.

A connecting pin 20 extends through the centers of rotation of the discs2a and 2b. The distance between the axis of the pin 20 and the axis ofthe pin 18 is equal to the distance between the axis of the pin 20 andthe axis of the pin 19, and the distance between the coupling pin andthe pivot pin is larger than the distance above described.

According to the structure of the tenth embodiment comprising thequadric crank mechanism of four link bars and two discs, the number ofrequired parts is small, and the apparatus of simple construction canyet efficiently achieve the desired object.

What is claimed is:
 1. A vibration damping apparatus comprising tworotatable members disposed opposite to each other while defining a gaptherebetween so as to be rotatable relative to each other aroundsubstantially a single axis of rotation, a resistive body disposed inthe gap between said rotatable members, and four pairs of link bars,each link in each pair of link bars being pivoted to each other at oneend thereof by a pin and coupled to said rotatable members in such arelation that the end of one of said link bars in each pair and the endof the adjoining one of said link bars in the next adjacent pair arecoupled by pin means to the associated one of said rotatable members. 2.A vibration damping apparatus as claimed in claim 1, wherein saidresistive body comprises a high viscosity material.
 3. A vibrationdamping apparatus as claimed in claim 1, wherein said resistive bodycomprises a resilient member.
 4. A vibration damping apparatus asclaimed in claim 1, wherein said resistive body comprises a combinationof a high viscosity material and a resilient member.
 5. A vibrationdamping apparatus as claimed in claim 1, wherein said pin means includesa single pin.
 6. A vibration damping apparatus as claimed in claim 1,wherein said pin means includes a pair of pins.